1. Field of the Invention
The present invention relates to a coating film removal apparatus and a coating film removal method for removing an unnecessary coating film at an edge portion of a quadrangular substrate on which the coating film is formed.
2. Description of the Background Art
In a process for manufacturing a semiconductor device, an exposure mask is formed in the following manner. First, a resist liquid is applied to a quadrangular mask substrate. Then, the resist film is exposed using a photomask and thereafter developed, thus fabricating a desired resist pattern. The resist liquid is applied to the mask substrate using spin coating, however, the resist liquid inevitably has a locally large thickness at a peripheral portion of the substrate, due to surface tension or the like. Accordingly, the resist film at the peripheral portion is not completely removed but left when developed, and the remaining resist peels off while the substrate is conveyed, which results in particles.
In view of the foregoing, after the resist liquid or the like is applied to a surface of the substrate, a treatment for removing an unnecessary coating film at an edge portion outside a pattern forming region on the substrate is carried out. Known examples of such a treatment include a method including the steps of holding a quadrangular substrate on a chuck, moving back and forth an arm portion with a washing block along an edge of the substrate, and removing a resist liquid film using a solvent fed from the arm portion (Japanese Patent Laying-Open No. 11-160891), and a method including the steps of using a carrier arm serving for loading/unloading a substrate in/out of a coating film forming apparatus so as to hold the substrate, and moving back and forth the substrate several times along a coating film removal portion equipped with a solvent feeding portion, so as to remove a resist liquid film (Japanese Patent Laying-Open No. 11-76908).
According to the invention in Japanese Patent Laying-Open No. 11-160891, the arm portion is moved back and forth, a solvent feeding pipe provided in the arm portion feeds a solvent, and a discharge pipe serves for suction and discharge of the solvent and dissolved coating film, so as to remove the coating film at the edge portion of the substrate.
In order to suck the solvent while the arm portion is being moved rapidly for ensuring a throughput so that the solvent fed to the edge portion of the substrate is quickly sucked for preventing introduction into the inner portion of the substrate, a discharge amount should be large, and preferably the discharge pipe has a large diameter. In the arm portion, a plurality of pipes and cables such as the solvent feeding pipe, a purge gas feeding pipe and the discharge pipe are provided in a complicated manner, and a large number of pipes and cables are routed. Accordingly, if the discharge pipe has a large diameter, large tension is applied to the arm portion. In addition, a driving portion with large power is required in order to drive such an arm portion. Further, each pipe or cable of a length adapted to movement of the arm portion should be provided, which also requires a space for routing these pipes and cables.
On the other hand, the discharge pipe bends as the arm portion moves. Depending on a position of the arm portion, however, a degree of bending varies. Hence, a discharge amount fluctuates corresponding to the degree of bending of the discharge pipe, leading to unstable discharge. That is, it has been difficult to remove the coating film in a stable manner.
In order to remove the coating film, the edge portion of the substrate should be moved back and forth a plurality of times with the edge portion lying between the coating film removal portions. According to the invention in Japanese Patent Laying-Open No. 11-76908, however, the substrate is moved by the carrier arm serving for loading/unloading the substrate in/out of the coating film forming apparatus, which means that the carrier arm is dedicated for such a removal operation. Then, its primary operation to carry the substrate itself is suspended, resulting in lower throughput.
Moreover, following problems also arise in addition to the disadvantages described above. It is preferable to provide in the arm portion a plurality of solvent nozzle portions such as a first solvent nozzle portion and a second solvent nozzle portion along a direction in which the substrate is moved forward, instead of providing a single solvent nozzle portion. If the first solvent nozzle portion and the second solvent nozzle portion are provided, for example, the solvent nozzle portion in the front mainly serves to dissolve the coating film, while the solvent nozzle portion in the rear mainly serves to blow away the dissolved coating film. On the other hand, in order to remove the coating film, the arm portion should move back and forth along the edge portion of the substrate a plurality of times. Therefore, a scanning speed of the arm portion should not be too slow to ensure throughput. If a space between the first solvent nozzle portion and the second solvent nozzle portion is too narrow, the dissolved coating film tends to be blown away while dissolving is not sufficiently achieved. Then, a washing effect is lowered, resulting in a larger number of scanning operations of the arm portion. Accordingly, the space between the nozzle portions is set so as not to be smaller than a certain value.
Recently, it has been demanded that a removal width of the coating film at the edge portion of the substrate is partially made larger than normal width. That is, it has been demanded that a removal area of the coating film is partially enlarged toward inside of the substrate. A conventional apparatus, however, has not been able to satisfy such a demand.